Extremely low duty-cycle activation of the cholinergic anti-inflammatory pathway to treat chronic inflammation

ABSTRACT

Described herein are systems and methods for applying extremely low duty-cycle stimulation sufficient to treat chronic inflammation using feedback to adjust the off times between stimulations. In particular, the feedback include an assessment of the level of inflammation by the patient or the healthcare provider, or by measure the level of an inflammatory analyte or biomarker, or by detecting nerve activity correlated with inflammation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/968,702, filed Dec. 14, 2015, titled “EXTREMELY LOW DUTY-CYCLEACTIVATION OF THE CHOLINERGIC ANTI-INFLAMMATORY PATHWAY TO TREAT CHRONICINFLAMMATION,” now U.S. Pat. No. 9,849,286, which is a continuation ofU.S. patent application Ser. No. 14/336,942, filed Jul. 21, 2014, titled“EXTREMELY LOW DUTY-CYCLE ACTIVATION OF THE CHOLINERGICANTI-INFLAMMATORY PATHWAY TO TREAT CHRONIC INFLAMMATION,” now U.S. Pat.No. 9,211,410, which is a continuation-in-part of U.S. patentapplication Ser. No. 13/467,928, filed May 9, 2012, titled “SINGLE-PULSEACTIVATION OF THE CHOLINERGIC ANTI-INFLAMMATORY PATHWAY TO TREAT CHRONICINFLAMMATION,” now U.S. Pat. No. 8,788,034, which claims the benefit ofU.S. Provisional Patent Application No. 61/484,112, filed May 9, 2011,and titled “SINGLE-PULSE ACTIVATION OF THE CHOLINERGIC ANTI-INFLAMMATORYPATHWAY TO TREAT CHRONIC INFLAMMATION,” each of which is herebyincorporated by reference in its entirety.

This patent application may be related to any of the following patentand pending patent applications: U.S. patent application Ser. No.12/434,462, filed May 1, 2009, titled “VAGUS NERVE STIMULATIONELECTRODES AND METHODS OF USE,” Publication No. US-2009-0275997-A1; U.S.patent application Ser. No. 12/620,413, filed Nov. 17, 2009, entitled“DEVICES AND METHODS FOR OPTIMIZING ELECTRODE PLACEMENT FORANTI-INFLAMMATORY STIMULATION,” now U.S. Pat. No. 8,412,338; U.S. patentapplication Ser. No. 12/874,171, filed Sep. 1, 2010, titled“PRESCRIPTION PAD FOR TREATMENT OF INFLAMMATORY DISORDERS,” PublicationNo. US-2011-0054569-A1; U.S. patent application Ser. No. 12/917,197,filed Nov. 1, 2010, titled “MODULATION OF THE CHOLINERGICANTI-INFLAMMATORY PATHWAY TO TREAT PAIN OR ADDICTION,” Publication No.US-2011-0106208-A1; U.S. patent application Ser. No. 12/978,250, filedDec. 23, 2010, titled “NEURAL STIMULATION DEVICES AND SYSTEMS FORTREATMENT OF CHRONIC INFLAMMATION,” now U.S. Pat. No. 8,612,002; andU.S. patent application Ser. No. 12/797,452, filed Jun. 9, 2010 andentitled “NERVE CUFF WITH POCKET FOR LEADLESS STIMULATOR,” PublicationNo. US-2010-0312320-A1.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference in their entirety to the sameextent as if each individual publication or patent application wasspecifically and individually indicated to be incorporated by reference.

FIELD

The present invention relates generally to systems and devices fortreatment of disorders, including chronic inflammation and inflammatorydisorders using extremely low duty-cycle stimulation. In particular,described herein are systems, devices and methods for treating disorderssuch as intestinal inflammatory disorders. Further described hereingenerally are methods and devices, including an implantablemicrostimulators, adapted for electrically stimulating the vagus nerveto treat chronic inflammation by extremely low duty cycle stimulation tomodulate an inflammatory response (via the nicotinic cholinergicanti-inflammatory pathway). In particular, described herein are systemsand method adapted to increase the duration between stimulations (“offtime”) while sustaining and even increasing the duration of equivalentinhibition.

BACKGROUND

Electrical stimulation of the neural cholinergic anti-inflammatorypathway (CAP or NCAP) has been described in the literature, beginningwith the seminal work of Kevin Tracey (see, e.g., Tracey, K J“Physiology and immunology of the cholinergic antiinflammatory pathway.”The Journal of clinical investigation 2007:117 (2): 289-96), who firstidentified the cholinergic anti-inflammatory pathway and characterizedthe link between vagus nerve stimulation and inhibition of inflammationby suppressing cytokine production. Since then, research as continued toexplore the relationship between stimulation of the CAP and modulationof inflammatory disorders. Typical stimulation parameters have includestimulation by a burst of pulses (e.g., between 10 Hz to 1 GHz forbetween 30 sec and 20 min), with a slight increase in effect seen athigher frequencies (see, e.g., U.S. Publication No. 2009/0143831 toHuston et al.).

Although this work has suggested that chronic inflammation may besuccessfully treated by an implantable stimulator, the design andimplementation of such a chronically implantable and usable stimulatorhas proven elusive, in part because of the power demands that a devicecapable of truly long-term, chronic, usage would face.

Implantable electrical stimulation devices have been developed fortherapeutic treatment of a wide variety of diseases and disorders. Forexample, implantable cardioverter defibrillators (ICDs) have been usedin the treatment of various cardiac conditions. Spinal cord stimulators(SCS), or dorsal column stimulators (DCS), have been used in thetreatment of chronic pain disorders including failed back syndrome,complex regional pain syndrome, and peripheral neuropathy. Peripheralnerve stimulation (PNS) systems have been used in the treatment ofchronic pain syndromes and other diseases and disorders. Functionalelectrical stimulation (FES) systems have been used to restore somefunctionality to otherwise paralyzed extremities in spinal cord injurypatients.

Recently, implantable vagus nerve stimulations have been developed,including vagus nerve stimulators to treat inflammation. Such implantstypically require an electrode and a power source. The size anduse-limiting parameters may typically be the power requirements, whicheither require a long-lasting (and therefore typically large) battery,or require the added complication of charging circuitry and chargingdevices.

For example, typical implantable electrical stimulation systems mayinclude one or more programmable electrodes on a lead that are connectedto an implantable pulse generator (IPG) that contains a power source andstimulation circuitry. Even relatively small implantable neuralstimulator technology, i.e. microstimulators, having integral electrodesattached to the body of a stimulator may share some of thesedisadvantages, as the currently developed leadless devices tend to belarger and more massive than desirable, making it difficult to stablyposition such devices in the proper position with respect to the nerve.

We herein describe the surprising result that long-lasting, robustinhibition of inflammation may be achieved by on a single (or very few)supra-threshold electrical pulse applied to the vague nerve. Thisfinding is particularly surprising given the extraordinarily robusteffect despite the minimal power applied, particularly compared topublished data showing effects at much higher applied energy. Thesefindings support various extremely low-power devices, system and methodsfor treating chronic inflammation. In particular, devices and methodsfor the treatment of inflammatory disorders, including inflammatorydisorders of the intestine (e.g., irritable bowel disorder or IBD) aredescribed, including microstimulators and methods of using them based onthe remarkably low power requirements identified.

SUMMARY OF THE DISCLOSURE

Described herein are devices, systems and methods for theextraordinarily low duty cycle stimulation of the vagus nerve. Anextraordinarily low, extremely low, super low, or ultra low duty cyclerefers generally to a duty cycle that provides stimulation using both alow number of electrical pulses per time period and a low stimulationintensity such that power requirements of the duty cycle are very low.The following are examples of various embodiments of extraordinarilylow, extremely low, super low, or ultra low duty cycles. In someembodiments, the number of electrical pulses can be between 1 and 5, inone pulse increments, every 4 to 48 hours (or every 48-72 hours, or ever2-4 days, or every 2-5 days, or every 2-10 days, or every 2-14 days orevery 2-18 days, or every 2-20 days or every 2-25 days, etc.), includingin 4 hour increments. In some embodiments, the stimulation intensity canbe at a supra-threshold level that is capable of effecting the desiredphysiological response through the vagus nerves. In some embodiments,the supra-threshold level is between about 100 μA and 5000 μA, orbetween about 100 μA and 4000 μA, or between about 100 μA and 3000 μA,or between about 100 μA and 2000 μA. In some embodiments, thesupra-threshold level is less than about 2000 μA, 3000 μA, 4000 μA or5000 μA.

In some embodiments, the duty cycle is one supra-threshold pulse every 4hours, with the pulse amplitude less than about 2000 μA. In someembodiments, the duty cycle is one pulse every 4 hours, with the pulseamplitude less than about 3000 μA. In some embodiments, the duty cycleis one pulse every 12 hours, with the pulse amplitude less than about2000 μA. In some embodiments, the duty cycle is one pulse every 12hours, with the pulse amplitude less than about 3000 μA. In someembodiments, the duty cycle is one pulse every 24 hours, with the pulseamplitude less than about 2000 μA. In some embodiments, the duty cycleis one pulse every 24 hours, with the pulse amplitude less than about3000 μA. In some embodiments, the duty cycle is one pulse every 48hours, with the pulse amplitude less than about 2000 μA. In someembodiments, the duty cycle is one pulse every 48 hours, with the pulseamplitude less than about 3000 μA.

In some embodiments the pulse width can be between about 100 to 1000 μS,or can be about or less than about 100, 200, 300, 400, 500, 600, 700,800, 900 or 1000 μS. In some embodiments, the frequency can be about orless than about 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 Hz. In someembodiments, the IPI can be about or less than about 100, 200, 300, 400,500, 600, 700, 800, 900 or 1000 μS.

In some embodiments, a system for treating chronic inflammation and/oran inflammatory disorder in a subject is provided. The system includesan implantable microstimulator configured to apply a low duty-cyclestimulation to a vagus nerve, wherein the low duty-cycle stimulationprovides no more than a single supra-threshold pulse every four hours;and a controller configured to set a dose for the microstimulatorwherein the dose comprises the single supra-threshold pulse followed byan off-period of at least four hours. In some embodiments, theoff-period is at least 24 hours, or at least 48 hours, or between about4 to 48 hours, or between about 12 to 48 hours, or between about 24 to48 hours. In some embodiments, the single supra-threshold pulse has apulse amplitude of less than 5 mA, less than 3 mA, or less than 2 mA. Insome embodiments, the single supra-threshold pulse is biphasic. In someembodiments, the chronic inflammation is intestinal inflammation. Insome embodiments, the chronic inflammation is inflammatory boweldisease. In some embodiments, the chronic inflammation is Crohn'sdisease.

In some embodiments, a method of treating chronic inflammation and/orinflammatory disorders in a subject is provided. The method includesimplanting a microstimulator; and applying only a single supra-thresholdstimulus pulse from the microstimulator to the vagus nerve followed byan off-time of at least 4 hours. In some embodiments, the off-time is atleast 24 hours, at least 48 hours, or between about 4 to 48 hours, orbetween about 12 to 48 hours, or between about 24 to 48 hours. In someembodiments, the single supra-threshold stimulus pulse has a pulseamplitude of less than 5 mA, less than 3 mA, or less than 2 mA. In someembodiments, the single supra-threshold stimulus pulse is biphasic. Insome embodiments, the chronic inflammation is intestinal inflammation.In some embodiments, the chronic inflammation is inflammatory boweldisease. In some embodiments, the chronic inflammation is Crohn'sdisease.

Types of inflammatory disorders that may be treated as described hereininclude a variety of disease states, including diseases such as hayfever, atherosclerosis, arthritis (rheumatoid, bursitis, goutyarthritis, polymyalgia rheumatic, etc.), asthma, autoimmune diseases,chronic inflammation, chronic prostatitis, glomerulonephritis,nephritis, inflammatory bowel diseases, pelvic inflammatory disease,reperfusion injury, transplant rejection, vasculitis, myocarditis,colitis, etc.

Non-limiting examples of inflammatory disorders which can be treatedusing the present invention include appendicitis, peptic ulcer, gastriculcer, duodenal ulcer, peritonitis, pancreatitis, ulcerative colitis,pseudomembranous colitis, acute colitis, ischemic colitis,diverticulitis, epiglottitis, achalasia, cholangitis, cholecystitits,hepatitis, Crohn's disease, enteritis, Whipple's disease, allergy,anaphylactic shock, immune complex disease, organ ischemia, reperfusioninjury, organ necrosis, hay fever, sepsis, septicemia, endotoxic shock,cachexia, hyperpyrexia, eosinophilic granuloma, granulomatosis,sarcoidosis, septic abortion, epididymitis, vaginitis, prostatitis,urethritis, bronchitis, emphysema, rhinitis, pneumonitits,pneumoultramicroscopic silicovolcanoconiosis, alvealitis, bronchiolitis,pharyngitis, pleurisy, sinusitis, influenza, respiratory syncytial virusinfection, HIV infection, hepatitis B virus infection, hepatitis C virusinfection, herpes virus infection disseminated bacteremia, Dengue fever,candidiasis, malaria, filariasis, amebiasis, hydatid cysts, burns,dermatitis, dermatomyositis, sunburn, urticaria, warts, wheals,vasulitis, angiitis, endocarditis, arteritis, atherosclerosis,thrombophlebitis, pericarditis, myocarditis, myocardial ischemia,periarteritis nodosa, rheumatic fever, Alzheimer's disease, coeliacdisease, congestive heart failure, adult respiratory distress syndrome,meningitis, encephalitis, multiple sclerosis, cerebral infarction,cerebral embolism, Guillame-Barre syndrome, neuritis, neuralgia, spinalcord injury, paralysis, uveitis, arthritides, arthralgias,osteomyelitis, fasciitis, Paget's disease, gout, periodontal disease,rheumatoid arthritis, synovitis, myasthenia gravis, thyroiditis,systemic lupus erythematosis, Goodpasture's syndrome, Behcet's syndrome,allograft rejection, graft-versus-host disease, Type I diabetes, Type IIdiabetes, ankylosing spondylitis, Berger's disease, Reiter's syndrome,Hodgkin's disease, ileus, hypertension, irritable bowel syndrome,myocardial infarction, sleeplessness, anxiety and stent thrombosis.

The systems and methods described herein generally relate to systems anddevices for treatment of chronic inflammation and inflammatorydisorders. In particular, described herein are systems, devices andmethods for treating intestinal disorders and rheumatoid arthritis.Further described herein generally are methods and devices, including animplantable microstimulators, adapted for electrically stimulating thevagus nerve to treat chronic inflammation by extremely- or super-lowduty cycle stimulation and by extremely low treatment dose schedule tomodulate an inflammatory response (via the cholinergic anti-inflammatorypathway).

For example, any of the systems and methods described herein may includeor be specifically adapted and/or configured to deliver a treatmentregimen in which the delay between stimulation doses (including singlebursts and/or single pulses of supra-threshold stimulation) isprogressively increased from the start of stimulation so that subsequent(later) stimulation occurs with longer off-times than earlier doses,without substantially decreasing the inhibition of inflammation due tothe vagal stimulation. This effect may be referred to herein as‘training’ the subject or vagus nerve, as the later stimulation(following an initial training period) may achieve the same or even morerobust inhibition of inflammation with a longer duration between appliedvagal stimulation. In general, the effect of VNS stimulation describedherein may be referred to as an inhibition of the inflammatory response,and may include the inhibition of cytokines, or the increase ofanti-inflammatory cytokines, or both.

For example, described herein are systems for treating chronicinflammation in a subject that include: an implantable microstimulatorconfigured to apply a low duty-cycle stimulation to a vagus nerve; and acontroller adapted to set a dose regimen of progressively delayedsupra-threshold stimulus pulses for the microstimulator, wherein thedose regimen comprises a first dose comprising a supra-thresholdstimulus pulse followed by a first off-period of at least about 48hours, a second dose comprising a supra-threshold stimulation pulsefollowed by a second off-period that is longer than the firstoff-period, and a series of sequential doses each comprising asupra-threshold stimulation pulse followed by an off-period that islonger than the second off-period, wherein the supra-threshold stimuluspulses are configured to reduce a level of inflammation in the subject.

The first off-period is may be least about 72 hours, or 3.5 days, 4days, 5 days, 6 days or 7 days, etc., and the second off period may beat least about 1.1 to 3 times the first off period (e.g., 5 days, 6days, 7 days, 8 days, 9 days, 10 days, 11 days, 12 days, 13 days, 14days, etc.). For example, the second and/or subsequent off-periods maybe between about 1.1 and 2 times the first off period (e.g., 1.2 and 2.2times, etc.). In one example, illustrated below, the first off-period isabout 7 days and the second off period is at least about 10 days. Ingeneral, the off-period is the quiescent period during which nosupra-threshold (and/or no stimulation at all) is applied by the implantto the vagus. In general, the time of the first off period may bedetermined based on the amount of inhibition of inflammation. Forexample, the duration of the first off period and subsequent off periodsmay be determined by examining the level of inhibition of inflammation(of an inflammatory response) or of a marker for inflammation and/or theinflammatory response. For example, the off-period may extend untilinflammation or a marker for inflammation and/or the inflammatoryresponse (either ongoing or evoked from the subject) is a percentage ofthe native inflammation level or inflammatory response (e.g., aboveabout 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%), etc. Thus, forexample, the off-periods of the sequential doses may each at least abouttwo weeks. In some variations, the off-periods of the sequential dosesare ramped up to a predetermined length of time. Thus, for example, thesecond off-period may be longer than the first off-period and subsequentoff-periods may be longer still (progressively longer), but may approacha limit (e.g., of two weeks, 18 days, 3 weeks, 25 days, etc.). The limitmay be a maximum delay period. In general, in the methods andapparatuses described herein, the application of the ultra-lowduty-cycle stimulation at the progressive off-times described herein mayresult in a tonic (ongoing) inhibition of inflammation (or of markersfor inflammation) at an acceptable level. This may permit remarkablylow-power (or low-power consumption) devices that may be operated formany days, weeks or even months, without requiring power replacement orrecharging while maintaining efficacy.

As mentioned above, the first dose may comprise a single supra-thresholdstimulus pulse, or burst of pulses. A burst of pulses typically has aburst duration of less than about 5 minutes, less than about 4 min, 3min, 2 min, 1 min, etc.). One or more (including all) of the pulses inthe burst may be supra threshold. In some variations, for example, thedose (including the first dose) comprises a single burst ofsupra-threshold stimulus pulses.

Any of the devices and methods described herein may be configured tosense an indicator of the subject's inflammation or inflammatoryresponse. For example, a system may include an analyte detectorconfigured to measure a level of an inflammatory analyte in thesubject's blood or bodily fluids (e.g., the level of a marker of aninflammatory response). Some variations may include a sensor configuredto detect a measure of inflammation based on the electrical activity ofthe vagus nerve; thus any of these systems may include one or moreelectrodes to sense activity on the vagus nerve. In any of thesesystems, the system (e.g., the controller) may be configured to adjustthe doses (e.g., the second dose and/or subsequent doses) based on thelevel of inflammation in the subject, e.g., the level of inhibition ofinflammation in the subject. For example, a controller may be configuredto adjust the second dose and subsequent doses based on the level of aninflammatory analyte, and/or the controller may be configured to adjustthe second off-period based on the level of inflammation in the subject(e.g. the level of the inhibition of the inflammatory response).

The controller may be configured to adjust the second off period basedon the level an inflammatory analyte, e.g., based on the amount ofinhibition of the inflammatory response. As mentioned, themicrostimulator may include a sensing electrode configured to monitorvagus nerve activity; this activity may be analyzed (e.g., by themicrostimulator or remotely from the microstimulator, which may transmitand receive data and/or command information or instructions). Themicrostimulator may comprise a sensing electrode configured to monitorvagus nerve activity, and also a processor configured to process themonitored vagus nerve activity to determine a level of inflammationand/or the level of inhibition of inflammation.

Also described herein are methods of treating chronic inflammation in apatient by progressively increasing the off-times between stimulation.For example, a method may include: applying a single supra-thresholdstimulus from a microstimulator to a vagus nerve, wherein the deliveryof the stimulus is followed by a first off-time of at least about 48hours during which an inflammatory response is suppressed; and applyingsubsequent supra-threshold stimuli, wherein each subsequent stimulus isfollowed by an off-time of longer than 48 hours.

The step of applying the single supra-threshold stimulus may includeapplying a single burst of pulses, or a single supra-threshold pulse. Asmentioned above, the off-times may be predetermined as part of thedosing regimen (e.g., the first off-time may at least about 72 hours, 4days, 5 days, 6 days, 7 days, etc.). The first off-time may be, forexample, at least about 7 days. The subsequent off-times may bepredetermined and/or may be modified by one or more subject-specificparameters, including, for example, the level of inhibition of theinflammatory response for the subject. For example, after the first orsecond stimulation doses are applied, the subsequent off-times may be atleast about one to two weeks. As mentioned, the subsequent off times maybe ramped up from the first off-time to a longer predetermined length oftime (e.g., up to two weeks, 2.5 weeks, three weeks, 3.5 weeks, fourweeks, etc.).

In any of these variations, the method may include a step of determiningthe level of inflammation (or the level of inhibition of theinflammatory response) and adjusting the off-times following thesubsequent supra-threshold stimuli based on the level of inflammationand/or the level of inhibition of the inflammatory response. Forexample, the level of inflammation and/or inhibition of inflammation maybe estimated by monitoring vagus nerve activity; the off-times followingthe subsequent supra-threshold stimuli may be adjusted based on thelevel of inflammation and/or the level of inhibition of inflammation.

In general, any of these methods may also include determining the levelof an inflammatory analyte in the subject's blood or bodily fluids andadjusting the off-times following the subsequent supra-threshold stimulibased on the level of analyte. The level of the analyte may beindicative of the level of inflammation and/or the level of inhibitionof inflammation. For example, a level of inhibition of inflammation maybe determined by comparison to a baseline (e.g., prior to vagus nervestimulation as described). The level of inhibition of inflammation maybe determined as a percentage of inhibition of this inflammatoryresponse. The inflammatory response may be determined by evoking (e.g.,ex vivo or in vivo) an inflammatory response and comparing it to acurrent (or some post-stimulation) time point.

Also described herein are methods of treating chronic inflammation in asubject by progressively increasing the off-times between stimulation.For example, a method may comprise: applying to a vagus nerve from animplanted microstrimulator, a first dose comprising a supra-thresholdstimulus, followed by a first off-time of at least about 48 hours,wherein the application of the first dose reduces the level ofinflammation in the subject; applying a second dose comprising asupra-threshold stimulus, followed by a second off-time that is longerthan the first off-time; and applying subsequent doses comprisingsupra-threshold stimuli, wherein each does is followed by an off-timethat is longer than the second off-time.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe claims that follow. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 is a diagram of a single stimulation waveform;

FIG. 2 is a graph comparing the effect on TNF levels from a singlestimulation pulse with the effect from up to 3000 pulses;

FIG. 3 is a graph illustrating the effect on TNF levels from a singlestimulation pulse 24 hours post-stimulation;

FIG. 4 is a graph illustrating the effect on TNF levels from a singlestimulation pulse 3 hours and 24 hours post-stimulation;

FIG. 5 is a graph illustrating the effect on lesion area in a rat modelof IBD from a single stimulation pulse;

FIG. 6 is a graph illustrating the long term effect on lesion area in arat model of IBD from a single stimulation pulse;

FIG. 7 is a diagram of an embodiment of a stimulation waveform;

FIGS. 8A and 8B illustrate an embodiment of a nerve cuff lead that hasbeen implanted around the vagus nerve;

FIG. 8C illustrates an embodiment of a microstimulator; and

FIG. 9 presents canine data that shows that vagus nerve stimulation canachieve a long lasting anti-inflammatory effect and that the longevityof the effect can be increased.

FIG. 10 is another example of vagus nerve stimulation with progressivelylonger off-times between extremely low duty-cycle does from amicrostimulator on the vagus nerve. The percent inhibition ofinflammation may be determined from the level of an analyte in the bloodand/or vagus nerve activity, as described herein.

DETAILED DESCRIPTION

In general, described herein are systems, methods and devicesillustrating extraordinarily low duty cycle stimulation of the vagusnerve to treat a disorder. In particular, described herein are systems,methods and devices illustrating extraordinarily low duty cyclestimulation of the vagus nerve to reduce or prevent inflammation and theeffects of inflammation in a mammalian model. An extraordinarily low,extremely low, super low, or ultra low duty cycle refers generally to aduty cycle that provides stimulation using both a low number ofelectrical pulses per time period and a low stimulation intensity suchthat power requirements of the duty cycle are very low. The methodsdescribed herein apply various stimulation protocols that may be used tosignificantly reduce inflammation and/or the effects of inflammation.Simulation parameters that may be varied include the pulse shape (e.g.,sinusoidal, square, biphasic, monophasic, etc.) the duration ofstimulation, the on-time, the off-time, the inter-pulse interval, or thelike. One key factor examined herein is the number of supra-thresholdpulses. As shown herein, the stimulation of the vagus nerve with even asingle supra-threshold stimulus results in a significant andlong-lasting effect, even when compared to multiple stimulations. Thiseffect was particularly profound when examined using a rodent model forIBD.

The following are examples of various embodiments of extraordinarilylow, extremely low, super low, or ultra low duty cycles. In someembodiments, the number of electrical pulses can be between 1 and 5, inone pulse increments, every 4 to 48 hours, in 4 hour increments. In someembodiments, the stimulation intensity can be at a supra-threshold levelthat is capable of effecting the desired physiological response throughthe vagus nerves. In some embodiments, the supra-threshold level isbetween about 100 μA and 5000 μA, or between about 100 μA and 4000 μA,or between about 100 μA and 3000 μA, or between about 100 μA and 2000μA. In some embodiments, the supra-threshold level is less than about2000 μA, 3000 μA, 4000 μA or 5000 μA.

In some embodiments, the duty cycle is one supra-threshold pulse every 4hours, with the pulse amplitude less than about 2000 μA. In someembodiments, the duty cycle is one pulse every 4 hours, with the pulseamplitude less than about 3000 μA. In some embodiments, the duty cycleis one pulse every 12 hours, with the pulse amplitude less than about2000 μA. In some embodiments, the duty cycle is one pulse every 12hours, with the pulse amplitude less than about 3000 μA. In someembodiments, the duty cycle is one pulse every 24 hours, with the pulseamplitude less than about 2000 μA. In some embodiments, the duty cycleis one pulse every 24 hours, with the pulse amplitude less than about3000 μA. In some embodiments, the duty cycle is one pulse every 48hours, with the pulse amplitude less than about 2000 μA. In someembodiments, the duty cycle is one pulse every 48 hours, with the pulseamplitude less than about 3000 μA.

The examples described herein use a stimulator and stimulation controlpackage that was developed for use in driving vagus nerve stimulation.In some example, the stimulation is controlled by a software packagethat is configured to run on a microprocessor (e.g., personal computer)and to control output of an emulator/stimulator (which may be referredto as an “ITE” or integrated terminal emulator). Thus, the systemsdescribed herein may include logic (e.g., control logic) that may besoftware, firmware, and/or hardware to control the application ofstimulation. For example, in some variations, the parameters controllingstimulation and data acquisition may include: (1) selected stimulatingelectrode pair including a cathode and anode; (2) frequency in 1 Hzincrements; (3) Pulse Width (PW): 20-2,000 uS in 1 uS increments; (4)Pulse Amplitude (PA): ±0-5,000 uA in 3 uA increments; and (5)Inter-Pulse-Interval between phase A & B of waveform (IPI): 20-2,000 uSin 1 uS increments.

In addition to the exemplary parameters provided above, in someembodiments the PW can be between about 100 to 1000 μS, or can be aboutor less than about 100, 200, 300, 400, 500, 600, 700, 800, 900 or 1000μS. In some embodiments, the frequency can be about or less than about10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 Hz. In some embodiments, theIPI can be about or less than about 100, 200, 300, 400, 500, 600, 700,800, 900 or 1000 μS.

For example, the exemplary waveform shown on FIG. 1 is a biphasic(charge balanced) waveform 100 that includes two symmetric pulse widths102 (PW) separated by an inter-pulse interval 104 (IPI). The pulsewidths 102 have a pulse amplitude 106 (PA) that is also symmetric forthe first phase 108 (phase A) and the second phase 110 (phase B) of thebiphasic stimulus, with a negative pulse amplitude in phase A and apositive amplitude in phase B. This biphasic pulse is a single pulsethat includes both a positive and negative excursion. Other pulsewaveforms may be used. In some embodiments, the pulse waveforms may benon-biphasic and/or may have asymmetric pulse widths and/or asymmetricpulse amplitudes.

The stimulator may generate a pulse train on a pair of electrodes. Ingeneral, a does may include a single pulse (e.g., a single biphasicpulse) or a single burst including multiple pulses. The pulses may begenerated using a bipolar current source and can be capacitivelyisolated with >1 uF ceramic capacitors on both electrodes outputs.Compliance voltage can be set to as high as +/−18.8 volts.

The different experimental examples described herein show thatappropriate NCAP stimulation of the vagus nerve can be used to limit oreliminate the effects of intestinal inflammation, in particular in a ratmodel of colitis and a rat model of Crohn's disorder. Based on thisdata, a biphasic simulation at the parameters described above maysuccessfully treat intestinal inflammation in humans or other mammals.

In one example, mice (Male, BALB/c) were anesthetized and cuffelectrodes (0.3 mm ID, 0.5 mm inter-electrode distance; Microprobes,Gaithersburg, Md.) were placed around the left carotid sheath(containing the cervical vagus nerve) and secured by suture.Supra-threshold pulses (750 μA, 2000, 10 Hz) were applied in variousnumbers (0, 1, 10, 100, 300, 600, 3000). Afterwards, the electrode wasremoved and the wound stapled closed. Mice recovered for 3 hours, andthen were challenged with LPS (5 mg/kg; IP); these mice were sacrificed90 minutes post-LPS and serum TNF measured by ELISA to measure theeffects on inflammatory cytokines. As shown on FIG. 2, even a singlesupra-threshold stimulus resulted in a significant suppression of TNF at3 hours after treatment. Thus, the effect was long lasting and theeffect from a single pulse at 3 hours was equivalent to the effectgenerated by up to 3000 pulses.

A second similar experiment was conducted to examine the long lastingeffect of a single supra-threshold pulse on the cholinergicanti-inflammatory pathway (CAP). Mice (Male, BALB/c) were anesthetizedand cuff electrodes (0.3 mm ID, 0.5 mm inter-electrode distance;Microprobes, Gaithersburg, Md.) were placed around the left carotidsheath (containing the cervical vagus nerve) and secured by suture.Supra-threshold pulses (750 μA, 2000, 10 Hz) were applied in variousnumbers (0, 1, 600). Afterwards, the electrode was removed and the woundstapled closed. Mice recovered for 24 hours, and then were challengedwith LPS (5 mg/kg; IP); these mice were sacrificed 90 minutes post-LPSand serum TNF measured by ELISA to measure the effects on inflammatorycytokines. As shown on FIG. 3, a single supra-threshold stimulusresulted in a significant suppression of TNF at 24 hours after treatmentthat was equivalent to the effect generated by 600 pulses.

FIG. 4 combines selected portions of the results of the two experimentsdescribed above to show that single pulse stimulation of the NCAPeffects suppression of LPS-inducible TNF at 3 hours and 24 hourspost-stimulation at the same effectiveness as 600 pulses.

In another example, an experiment was conducted to determine theeffectiveness of single pulse suppression of lesion area in a rat modelfor IBD/Crohn's disease. Rats were anesthetized and were either given asham stimulation or a single supra-threshold stimulus to the leftcervical vagus nerve (1 pulse at 750 μA, 2000 pulse width, 10 Hz). IBDwas induced at 30 minutes post-stimulation by the SC injection ofindomethacin (10 mg/kg (5 mg/mL) in 5% sodium bicarbonate). Lesions werestained in-life 23.5 hours post-indomethacin injection by anesthetizingthe rats with isoflurane and IV tail injection with Evans Blue (0.3 mlof 1%). Rats were sacrificed via C02 asphyxiation at 24 hours postdisease induction, and the small intestines were harvested, cleaned andfixed in 2% formalin overnight. Photographs were taken and digitized ofthe fixed intestines and lesions were quantified by a blinded scorer. Asillustrated in FIG. 5, a single supra-threshold stimulus (750 μA, 2000pulse width, 10 Hz) resulted in a profound reduction in lesions.

These results are even more significant, given the data shown in FIG. 6,which illustrates a “memory effect” of vagus nerve stimulation in a ratmodel of Crohn's disease. Rats were anesthetized and were either given asham stimulation or an actual stimulation to the left cervical vagusnerve (1 mA, 2000 pulse width, 10 Hz, 60 s). IBD/Crohn's disease wasinduced at various times (see FIG. 6) post-stimulation by the SCinjection of indomethacin (10 mg/kg (5 mg/mL) in 5% sodium bicarbonate).Lesions were stained in-life 23.5 hours post-disease induction byanesthetizing the rats with isoflurane and IV tail injection with EvansBlue (0.3 ml of 1%). Rats were sacrificed via C0₂ asphyxiation at 24hours post disease induction, and the small intestines were harvested,cleaned and fixed in 2% formalin overnight. Photographs were taken anddigitized of the fixed intestines and lesions were quantified by ablinded scorer. In this example, a brief period of stimulation of thevagus nerve may result in a surprisingly long-lasting effect (e.g., upto 48 hours) in the reduction of intestinal lesions otherwise induced bythe application of indomethacin. This data strongly suggests thatstimulation may be provided extremely infrequently, with long (e.g., >48hours) of “silent” periods without stimulation applied. Such extremelylow duty-cycle stimulation for treating IBD may be particularly helpfulin implantable systems, allowing extremely long battery life whilehaving unexpectedly robust therapeutic benefits.

Although the examples provided above describe methods, systems anddevices for treating an inflammatory disorder in a rat model, all themethods, systems and devices described herein can be used and/or adaptedfor use in other mammals, such as humans. For example, a system andmethod for treating an inflammatory disorder in a human using a singlesupra-threshold pulse and/or an extraordinarily low duty cyclestimulation protocol can include an electrode, such as a cuff electrode,that is configured to be implanted around the vagus nerve and deliverelectrical stimulation to the vagus nerve of the subject. The system canfurther include a processor, memory for storing instructions, and/or acontroller can include programming to deliver the low duty cyclestimulation protocol, including the single supra-threshold pulseprotocol, to the vagus nerve via the cuff electrode. A battery can beprovided to provide power for the system, and because the low duty cyclestimulation protocol consumes so little energy, the battery life can begreatly extended, allowing the system to be completely implanted withinthe subject for a long duration before the battery needs to be replacedor recharged. For an implanted system, this provides a great benefitsince it can reduce the frequency of surgical procedures that may berequired to change the battery.

The stimulation parameters used in this system can be the same orsimilar to the parameters disclosed above. For example, the pulseamplitude can be less than about 5, 4, 3, or 2 mA. In addition, the lowduty cycle stimulation protocol can deliver a single supra-thresholdpulse between off-times of between about 4 to 48 hours, or at least 4,12, 24, or 48 hours. In some embodiments the pulse width can be betweenabout 100 to 1000 μS, or can be about or less than about 100, 200, 300,400, 500, 600, 700, 800, 900 or 1000 μS. In some embodiments, thefrequency can be about or less than about 10, 20, 30, 40, 50, 60, 70,80, 90 or 100 Hz. In some embodiments, the IPI can be about or less thanabout 100, 200, 300, 400, 500, 600, 700, 800, 900 or 1000 μS.

In general, these results suggest that the application of even a singlebrief supra-threshold stimulus of the vagus nerve may result in asubstantial reduction in the effects of inflammation, possibly byinhibition of inflammatory cytokines such as TNF. These results are bothsurprising, given the prior arts tendency to stimulate for much longertimes, and important for the design of future devices and methods. Inparticular, stimulation of the vagus nerve (or other portions of theinflammatory reflex) may be configured to apply extremely low duty-cyclestimulation. As mentioned briefly, this would allow for much smaller,lighter and more efficient implantable stimulation systems.

Another phenomenon seen in the experiments of FIGS. 2-7 is the trainingeffect in which subsequent vagus nerve stimulation, particularly withextremely low duty-cycle stimulation, results in increasing the durationof suppression of the inflammatory response in the patient. For example,in mice, as well as other mammals into which a microstimulator has beenapplied to the vagus nerve, the first application of a dose of a dosingregimen (and particularly an extremely low duty-cycle dose), e.g., asince burst of supra-threshold pulses, e.g., having a burst duration ofless than 5 min, 2 min, 1 min, etc., or even a single supra-thresholdpulse, results in an inhibition of inflammation that lasts for manyhours, and even days, as shown in FIG. 6. A second dose (e.g., pulse ofsupra-threshold stimulation) that is equivalent to the first pulseresults in a longer-lasting inhibition than the first dose. Subsequentstimulation may also result in longer-lasting inhibition than precedingsimulation. This means that the off-period between stimulation may beincreased with subsequent stimulation, as is seen, for example, in FIGS.9 and 10, discussed below. Preliminary data suggests that the lowerduty-cycle (e.g., single pulse/single burst of limited burst duration)stimulation may be most effective in creating this enhanced duration ofinhibition. When multiple (e.g., greater than 100 supra-thresholdpulses, greater than 90 supra-threshold pulses, greater than 80supra-threshold pulses, greater than 70 supra-threshold pulses, greaterthan 60 supra-threshold pulses, greater than 50 supra-threshold pulses,greater than 40 supra-threshold pulses, greater than 30 supra-thresholdpulses, greater than 25 supra-threshold pulses, greater than 20supra-threshold pulses, etc.) are used, significant enhancement of theduration of inhibition may not be robustly observed. Thus, it may bebeneficial to limit the number of pulses in dose to less than 100, 90,80, 70, 60, 50, 40, 30, 25, 20 etc. supra-threshold pulses, separated byan off-time of greater than 48 hours, 3 days, 4, days, etc.

Types of inflammatory disorders that may be treated as described hereininclude a variety of disease states, including diseases such as hayfever, atherosclerosis, arthritis (rheumatoid, bursitis, goutyarthritis, polymyalgia rheumatic, etc.), asthma, autoimmune diseases,chronic inflammation, chronic prostatitis, glomerulonephritis,nephritis, inflammatory bowel diseases, pelvic inflammatory disease,reperfusion injury, transplant rejection, vasculitis, myocarditis,colitis, etc.

Non-limiting examples of inflammatory disorders which can be treatedusing the present invention include appendicitis, peptic ulcer, gastriculcer, duodenal ulcer, peritonitis, pancreatitis, ulcerative colitis,pseudomembranous colitis, acute colitis, ischemic colitis,diverticulitis, epiglottitis, achalasia, cholangitis, cholecystitits,hepatitis, Crohn's disease, enteritis, Whipple's disease, allergy,anaphylactic shock, immune complex disease, organ ischemia, reperfusioninjury, organ necrosis, hay fever, sepsis, septicemia, endotoxic shock,cachexia, hyperpyrexia, eosinophilic granuloma, granulomatosis,sarcoidosis, septic abortion, epididymitis, vaginitis, prostatitis,urethritis, bronchitis, emphysema, rhinitis, pneumonitits,pneumoultramicroscopic silicovolcanoconiosis, alvealitis, bronchiolitis,pharyngitis, pleurisy, sinusitis, influenza, respiratory syncytial virusinfection, HIV infection, hepatitis B virus infection, hepatitis C virusinfection, herpes virus infection disseminated bacteremia, Dengue fever,candidiasis, malaria, filariasis, amebiasis, hydatid cysts, burns,dermatitis, dermatomyositis, sunburn, urticaria, warts, wheals,vasulitis, angiitis, endocarditis, arteritis, atherosclerosis,thrombophlebitis, pericarditis, myocarditis, myocardial ischemia,periarteritis nodosa, rheumatic fever, Alzheimer's disease, coeliacdisease, congestive heart failure, adult respiratory distress syndrome,meningitis, encephalitis, multiple sclerosis, cerebral infarction,cerebral embolism, Guillame-Barre syndrome, neuritis, neuralgia, spinalcord injury, paralysis, uveitis, arthritides, arthralgias,osteomyelitis, fasciitis, Paget's disease, gout, periodontal disease,rheumatoid arthritis, synovitis, myasthenia gravis, thyroiditis,systemic lupus erythematosis, Goodpasture's syndrome, Behcet's syndrome,allograft rejection, graft-versus-host disease, Type I diabetes, Type IIdiabetes, ankylosing spondylitis, Berger's disease, Reiter's syndrome,Hodgkin's disease, ileus, hypertension, irritable bowel syndrome,myocardial infarction, sleeplessness, anxiety and stent thrombosis.

Any of these disorders (e.g., inflammatory disorders) may be treated by,for example, implanting a cuff electrode around the vagus nerve, andusing an extraordinarily low duty cycle stimulation protocol asdescribed herein to treat. A processor and memory for storinginstructions and/or programming can be used to control the stimulationprotocol. The stimulation parameters used in this system and method canbe the same or similar to the parameters disclosed above. For example,the pulse amplitude of the single supra-threshold pulse can be less thanabout 5, 4, 3, or 2 mA. In addition, the low duty cycle stimulationprotocol can deliver a single supra-threshold pulse between off-times ofbetween about 4 to 48 hours, or at least 4, 12, 24, or 48 hours. Any ofthese methods may include a step of determining the efficacy of thetreatment. For example, any of these methods may include the step ofmonitoring the subject before and/or during treatment. For example, intreating an inflammatory disorder, a biomarker for inflammation may bemonitored, such as a cytokine or other marker. In some variations,monitoring the subject may include assessing the subject visually (e.g.,for swelling, body temperature, etc.). In some variations the systemsdescribed herein may include a sensor and/or data processing subsystemfor monitoring the subject and/or the effect of the treatment with thesystem.

Although the examples and description above focuses primarily oninflammatory disorders, in some embodiment, the systems, devices andmethods described herein can be used to treat non-inflammatory diseasesor disorders. For example, the systems, devices and methods describedherein can be used to activate, regulate, and/or modulate the levels ofsirtuins by extraordinarily low duty cycle stimulation of the vagusnerve. The modulation of sirtuins by vagus nerve stimulation is alsodiscussed in U.S. patent application Ser. No. 13/338,185, filed Dec. 27,2011, titled “MODULATION OF SIRTUINS BY VAGUS NERVE STIMULATION,”Publication No. US-2013-0079834-A1 which is hereby incorporated byreference in its entirety for all purposes. As above, a cuff electrodecan be implanted around the vagus nerve and a processor and memory forstoring instructions and/or programming can be used to control thestimulation protocol. The stimulation parameters used in this system andmethod can be the same or similar to the parameters disclosed above. Forexample, the pulse amplitude of the single supra-threshold pulse can beless than about 5, 4, 3, or 2 mA. In addition, the low duty cyclestimulation protocol can deliver a single supra-threshold pulse betweenoff-times of between about 4 to 48 hours, or at least 4, 12, 24, or 48hours. In some embodiments the pulse width can be between about 100 to1000 μS, or can be about or less than about 100, 200, 300, 400, 500,600, 700, 800, 900 or 1000 μS. In some embodiments, the frequency can beabout or less than about 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 Hz.In some embodiments, the IPI can be about or less than about 100, 200,300, 400, 500, 600, 700, 800, 900 or 1000 μS.

As mentioned above, in some embodiments, the system, device, and/ormethod includes monitoring the effects of the stimulation on the diseasebeing treated. For example, inflammation indicators or diseaseindicators or other indicators can be monitored to evaluate the efficacyof the treatment protocol, allowing the stimulation protocol to beadjusted based on the evaluation. Any one of the parameters describedherein can be modulated based on the evaluation. For example, the pulseamplitude and/or the off time can be increased or decreased to optimizethe treatment efficacy. Examples of indicators that can be monitoredinclude TNF levels, lesion size, degree or level of inflammation,cytokine levels, pain levels, sirtuin levels, and the like.

Another key factor examined herein is the longevity of effect of asingle stimulation as well as the increase in the longevity of effectfollowing a second stimulation that is applied after, for example, sevendays later. In other embodiments, the second stimulation is deliveredbetween 1-14 days after the first stimulation. In some embodiments, athird stimulation can be delivered 1-30 days after the secondstimulation. More generally, the time period between stimulations can beincreased after each stimulation until a desired or predetermined periodof time between stimulations is achieved. In some embodiments, the timeperiod between stimulations can be predetermined. The predetermined timeperiod between stimulations may be constant, or can increase over timeto a predetermined duration. In embodiments where the time periodbetween stimulations is increased over time, the increase can begradual, stepwise, or based according to a predetermined schedule. Forexample, the time period can be increased by 5, 10, 15, 20, or 25percent, or by about 5-25 percent over the previous time period.

In other embodiments, the time period can be based on a measurement ofanalyte levels, biomarker levels, an assessment of the level ofinflammation, and/or level or pattern or signature of vagus nerveactivity, such that the next stimulation is applied when the analytelevel, biomarker level, assessment of the level of inflammation, and/orlevel or pattern or signature of vagus nerve activity either exceeds orfalls below a predetermined threshold. The levels or presence ofanalytes and biomarkers can also be indicators for inflammation. Forexample, the analyte can be TNF or another inflammatory cytokine ormediator. In some embodiments, the inflammatory analyte or biomarker canbe measured ex vivo in a whole blood response assay or in another assayusing whole blood or blood plasma. The assessment of the level ofinflammation can also be a clinical assessment and/or a patientassessment, and can include a measurement and/or scoring of swellingand/or pain. In some embodiments, the measurements and/or assessmentscan be performed at predetermined intervals, such as daily, or every twodays, which can begin immediately or after a predetermined time haselapsed, such as after 1, 2, 3, 4, 5, 6, or 7 days, for example. Thelevel or pattern or signature of vagus nerve activity can also becorrelated with levels of inflammation, allowing level of inflammationto be determined by monitoring of vagus nerve electrical activity, whichcan be done with a microstimulator with electrical sensing leads andsignal processing circuitry and/or software, which can be on themicrostimulator or on a computing device in communication with themicrostimulator. In some embodiments, various combinations of the abovecan be used to increase the time period between stimulations.

The examples described herein may use a stimulator and stimulationcontrol package that was developed for use in driving vagus nervestimulation. In some examples, the stimulation is controlled by asoftware package that is configured to run on a microprocessor (e.g.,personal computer) and to control output of an emulator/stimulator(which may be referred to as an “ITE” emulator stimulator). Withreference to FIG. 7, the parameters controlling stimulation and dataacquisition may include: (1) selected stimulating electrode pairincluding a cathode and Anode; (2) frequency in 1 Hz increments; (3)Pulse Width (PW): 20-2,000 uS in 1 uS increments; (4) Pulse Amplitude(PA): ±0-5,000 uA in 3 uA increments; and (5) Inter-Pulse-Intervalbetween phase A & B of waveform (IPI): 20-2,000 uS in 1 uS increments.

For example, the exemplary waveform shown on FIG. 7 is a biphasic(charge balanced) waveform that includes two symmetric pulse widths (PW,one positive, one negative) separated by an inter-pulse interval (IPI).The pulse widths have a pulse amplitude (PA) that is also symmetric forthe first phase (phase A) and the second phase (phase B) of the biphasicstimulus. Other pulse waveforms may be used. Exemplary parameters for awaveform are shown in FIG. 7, which illustrates a waveform used in anexperiment described in more detail below, where the waveform had apulse width of 200 μsec, an inter-pulse-interval of 50 μsec, a pulseamplitude of 250-1000 μA, and a frequency of 20 Hz.

The stimulator may generate a pulse train on a pair of electrodes. Thepulses may be generated using a bipolar current source and can becapacitively isolated with >1 uF ceramic capacitors on both electrodesoutputs. Compliance voltage can be set to as high as +/−18.8 volts.

The stimulator may use traditional electrode configurations, such as acuff electrode 800 illustrated in FIG. 8A. Alternatively, the stimulatormay be a microstimulator 810 as illustrated in FIG. 8C, which is furtherdescribed in U.S. Pat. No. 8,612,002, which is herein incorporated byreference in its entirety.

As illustrated in the experimental example described below, appropriateNCAP stimulation of the vagus nerve can be used to limit the TNFinducibility of leukocytes in ex vivo blood by endotoxin, a reflectionof the inflammatory responsiveness of the subject. Based on this data, abiphasic simulation at the parameters described above may successfullytreat inflammatory disease, with progressively longer duration ofanti-inflammatory effect with each successive stimulation.

FIGS. 8A and 8B illustrate one example in which progressively longeroff-times were used to achieve a sustained inhibition of inflammation.Two canines (male, hound cross, about 1 years old) were anesthetized andnerve cuff electrodes 200 (Evergreen Medical, Minneapolis, Minn.) wereplaced around the cervical vagus nerve, as illustrated in FIGS. 8A and8B. The lead body was externalized and protected under a jacket.Supra-threshold electrical pulses (250-1000 μA, 2000, 20 Hz, total of600 stimuli per burst) were applied seven days apart. Blood was drawnabout every three days, and the drawn blood was challenged withendotoxin ex vivo (0.1-0.5 ng/mL LPS) for four hours; the serum TNFlevels were measured by ELISA to measure the effects on inflammatorycytokines.

As shown on FIG. 9, even a single 60 second stimulation of the vagusnerve resulted in a substantial suppression of TNF for at least 7 days.Thus, the initial effect was very long lasting. Additionally, when thecanines were stimulated for a second time, the same second 60 secondstimulation following upon the resulted in suppression ofendotoxin-induced TNF for an even longer period of time, about 9-12days. Thus, the anti-inflammatory effect was trainable to provideprogressively increased longevity or duration of anti-inflammatoryeffect with each successive stimulation. Although the data in FIG. 9 aredoses that each include a single burst of supra-threshold pulses (e.g.,600 per dose), the number of pulses may be different, and may besingle-pulse. Although the onset of the effect of single pulse onmarkers for an anti-inflammatory (and/or inhibition of inflammation)response, the duration and extent of the effect is typically the same asthat seen for multiple pulses (as discussed above for FIGS. 2-6).

These data illustrate an extremely persistent anti-inflammatory effectof vagus nerve stimulation on the blood of a large mammal with just asingle stimulation dose. In this example, a single brief period ofstimulation of the vagus nerve results in a surprisingly long-lastingeffect (e.g., up to 7 days). Importantly, the persistence of this effectmay be lengthened by training the inflammatory system through infrequentstimulations, potentially allowing for effective stimulations to bedelivered weekly, monthly, every two months, quarterly or even annually.This data strongly suggests that stimulation may be provided extremelyinfrequently, with long (e.g., >48 h, >7 days) “silent” periods withoutstimulation applied. Such extremely low duty-cycle stimulation fortreating IBD or rheumatoid arthritis and other diseases mediated by theinflammatory pathway may be particularly helpful in implantable systems,allowing extremely long battery life while having unexpectedly robusttherapeutic benefits.

In general, these results suggest that the application of even a singlebrief stimulus (or burst of stimulus) of the vagus nerve may result in asubstantial long term reduction in the effects of inflammation.Furthermore, these results suggest that the duration of theanti-inflammatory effect of the single stimulation may be increased byapplying subsequent stimulations after a relatively lengthy period oftime between stimulations. These results are surprising, given the priorarts tendency to stimulate for much longer times, and important for thedesign of future devices and methods. In particular, stimulation of thevagus nerve (or other portions of the inflammatory reflex) may beconfigured to apply extremely low duty-cycle stimulation. As mentionedbriefly, this would allow for much smaller, lighter and more efficientimplantable stimulation systems.

FIG. 10 illustrates a prophetic example of a dosing regimen that maymaximize the progressively longer off times described above. In FIG. 10,a baseline of 0% inhibition of inflammation is shown prior to startingthe stimulation from the implanted microstimulator. At t=0 (day 0), thefirst dose is applied. As mentioned, the first dose maybe a singlesupra-threshold pulse, or a single burst (e.g., 1 min, 2 min, 5 min)burst of supra-threshold stimulation, followed by an enforced off-timeperiod, when stimulation is not applied. By day 7, the percentinhibition of inflammation has fallen back to nearly 25% inhibition.Thereafter, a second dose is applied (dose 2), driving inhibition backup. In this example, the inhibition following the second extremelylow-duty cycle stimulation (does 2 may be the same or different as theelectrical stimulation applied by dose 1) is longer-lasting thatfollowing the single dose, allowing a longer off-time period before thepercent inhibition falls back to nearly 25% again at day 18(approximately 10-11 days following dose 2). The third stimulation doseis applied, and the percent inhibition again takes even longer (e.g.,14-15 days) to fall back to nearly 25% inhibition of inflammation.Subsequent additional doses may be applied to sustain the inhibition ofinflammation, as illustrated for doses 4 and 5 (or more); the off-timeduration may continue to be reduced down to a maximum predetermined offtime (e.g., 25 days, 28 days, 30 days, etc.).

When a feature or element is herein referred to as being “on” anotherfeature or element, it can be directly on the other feature or elementor intervening features and/or elements may also be present. Incontrast, when a feature or element is referred to as being “directlyon” another feature or element, there are no intervening features orelements present. It will also be understood that, when a feature orelement is referred to as being “connected”, “attached” or “coupled” toanother feature or element, it can be directly connected, attached orcoupled to the other feature or element or intervening features orelements may be present. In contrast, when a feature or element isreferred to as being “directly connected”, “directly attached” or“directly coupled” to another feature or element, there are nointervening features or elements present. Although described or shownwith respect to one embodiment, the features and elements so describedor shown can apply to other embodiments. It will also be appreciated bythose of skill in the art that references to a structure or feature thatis disposed “adjacent” another feature may have portions that overlap orunderlie the adjacent feature. Terminology used herein is for thepurpose of describing particular embodiments only and is not intended tobe limiting of the invention. For example, as used herein, the singularforms “a”, “an” and “the” are intended to include the plural forms aswell, unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “comprises” and/or “comprising,” when used inthis specification, specify the presence of stated features, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, steps, operations,elements, components, and/or groups thereof. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items and may be abbreviated as “/”.

Spatially relative terms, such as “under”, “below”, “lower”, “over”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if a device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus, the exemplary term “under” can encompass both anorientation of over and under. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly”, “downwardly”, “vertical”, “horizontal” and the like are usedherein for the purpose of explanation only unless specifically indicatedotherwise.

Although the terms “first” and “second” may be used herein to describevarious features/elements (including steps), these features/elementsshould not be limited by these terms, unless the context indicatesotherwise. These terms may be used to distinguish one feature/elementfrom another feature/element. Thus, a first feature/element discussedbelow could be termed a second feature/element, and similarly, a secondfeature/element discussed below could be termed a first feature/elementwithout departing from the teachings of the present invention.

As used herein in the specification and claims, including as used in theexamples and unless otherwise expressly specified, all numbers may beread as if prefaced by the word “about” or “approximately,” even if theterm does not expressly appear. The phrase “about” or “approximately”may be used when describing magnitude and/or position to indicate thatthe value and/or position described is within a reasonable expectedrange of values and/or positions. For example, a numeric value may havea value that is +/−0.1% of the stated value (or range of values), +/−1%of the stated value (or range of values), +/−2% of the stated value (orrange of values), +/−5% of the stated value (or range of values), +/−10%of the stated value (or range of values), etc. Any numerical rangerecited herein is intended to include all sub-ranges subsumed therein.For example, as used herein, “about” and “approximately” can mean within5, 10, 15, 20, 25, or 30 percent.

Although various illustrative embodiments are described above, any of anumber of changes may be made to various embodiments without departingfrom the scope of the invention as described by the claims. For example,the order in which various described method steps are performed mayoften be changed in alternative embodiments, and in other alternativeembodiments one or more method steps may be skipped altogether. Optionalfeatures of various device and system embodiments may be included insome embodiments and not in others. Therefore, the foregoing descriptionis provided primarily for exemplary purposes and should not beinterpreted to limit the scope of the invention as it is set forth inthe claims.

The examples and illustrations included herein show, by way ofillustration and not of limitation, specific embodiments in which thesubject matter may be practiced. As mentioned, other embodiments may beutilized and derived there from, such that structural and logicalsubstitutions and changes may be made without departing from the scopeof this disclosure. Such embodiments of the inventive subject matter maybe referred to herein individually or collectively by the term“invention” merely for convenience and without intending to voluntarilylimit the scope of this application to any single invention or inventiveconcept, if more than one is, in fact, disclosed. Thus, althoughspecific embodiments have been illustrated and described herein, anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

What may be claimed is:
 1. A system for treating chronic inflammation ina subject, the system comprising: an implantable microstimulatorconfigured to apply a low duty-cycle stimulation to a vagus nerve; and acontroller adapted to set a dose regimen, wherein the dose regimencomprises a plurality of electrical stimulations to the vagus nerve thatare separated by an off period of at least 4 hours, wherein eachelectrical stimulation comprises less than 100 supra-threshold pulses.2. The system of claim 1, wherein each electrical stimulation comprisesless than 20 supra-threshold pulses.
 3. The system of claim 1, whereineach electrical stimulation comprises less than 5 supra-thresholdpulses.
 4. The system of claim 1, wherein the off period is adjustable.5. The system of claim 1, wherein the off period is adjustable based onfeedback from a sensor that is configured to measure an indicator of alevel of inflammation.
 6. The system of claim 1, wherein the off periodis at least 24 hours.
 7. The system of claim 1, wherein the off periodis at least 48 hours.
 8. The system of claim 1, wherein eachsupra-threshold pulse has a pulse amplitude of less than 5 mA.
 9. Thesystem of claim 1, wherein each supra-threshold pulse has a pulseamplitude of less than 3 mA.
 10. The system of claim 1 wherein eachsupra-threshold pulse has a pulse amplitude of less than 2 mA.
 11. Amethod of treating chronic inflammation in a patient, the methodcomprising: implanting a microstimulator; and applying an electricalstimulation comprising no more than 100 supra-threshold stimulus pulsesfrom the microstimulator to the vagus nerve followed by an off-time ofat least 4 hours; and reducing a level of inflammation in the patient.12. The method of claim 11, wherein the off-time is at least 24 hours.13. The method of claim 11, wherein the off-time is at least 48 hours.14. The method of claim 11, wherein each supra-threshold stimulus pulsehas a pulse amplitude of less than 5 mA.
 15. The method of claim 11,wherein each supra-threshold stimulus pulse has a pulse amplitude ofless than 3 mA.
 16. The method of claim 11, wherein each supra-thresholdstimulus pulse has a pulse amplitude of less than 2 mA.
 17. The methodof claim 11, wherein the electrical stimulation comprises less than 20supra-threshold pulses.
 18. The method of claim 11, wherein theelectrical stimulation comprises less than 5 supra-threshold pulses. 19.The method of claim 11, further comprising: measuring an indicator of alevel of inflammation; and adjusting the off period.